Cuppa tea anyone?
‘There is no trouble so great or grave that cannot be much diminished by a nice cup of tea’ so the saying goes. Now it looks like that very same cuppa may help quell blood glucose spikes. A one gram cup of black tea may have the potential to stimulate an insulin response and reduce blood glucose levels, report Judith Bryans and colleagues from King's College London and the University of Central Lancashire in the Journal of the American College of Nutrition. Their findings suggest that black tea could blunt blood glucose spikes, keeping the body's blood glucose levels relatively steady throughout the day. They recruited 16 healthy volunteers for a randomised, crossover study and assigned them 75 grams of glucose in either 250 ml of water (control), 250 ml of water plus 0.052 g of caffeine (positive control) or 250 ml of water plus 1.0 gram (1½ teaspoons) of instant black tea. For the first hour after drinking the beverages the glucose concentrations did not differ much at all among the volunteers. However, after two hours tea drinkers’ glucose levels were significantly reduced compared with the controls. Tea drinking also showed elevated insulin concentrations at 1½ hours compared to the controls – the likely reason for the observed decrease in blood glucose levels. In a cautious conclusion the researchers point out that: ‘the physiological effects … were relatively small and were achieved under test conditions. Under normal tea drinking conditions before or after food, the presence of other phenolic compounds could potentially alter, or even enhance, the effects seen in our study.’
– Journal of the American College of Nutrition, 26 (5), 2007
Veggie fibre does it
If you want to reduce your risk of diabetes, eat a low GI diet and tuck into your veggies (especially legumes) say University of Sydney researchers writing in the November edition of Diabetes Care. The study which tracked more than 2,100 Australians over 10 years found that veggie fibre offers more protection against diabetes than fruit or cereal fibre reducing the risk of developing type 2 diabetes by 24%. Diets high in fruit or cereal fibre weren’t nearly as beneficial. In a separate analysis of people aged less than 70 years, diets with a high GI increased their risk of developing type 2 diabetes by 75%, compared with those eating a low GI diet.
Talking to GI News, the study leader, Alan Barclay, said: ‘vegetables, and legumes in particular, were probably delivering the best results because they were an ideal source of intact or natural fibre. Legumes like beans, lentils and chickpeas and vegetables like sweet corn, carrots and peas are eaten whole with their dietary fibre intact, which means they actually encapsulate the carbohydrate in the food. They therefore slow down the rate of digestion and absorption and have good flow-on glycemic effects on blood glucose. Cereal fibre was not so effective because it is now often added to products, rather than eaten in a natural form. And while fresh fruit fibre is often eaten intact, people probably just did not get enough from the fruit they eat to show a benefit.’
– Diabetes Care, Vol 30, No 11, November 2007
Source: Ontario Beans
What about fibre and GI?
Dietary fibre is not one chemical constituent like fat and protein. It is composed of many different sorts of molecules and can be divided into soluble and insoluble types. The effect of fibre on a food’s GI depends on the type of fibre. Soluble fibres are the gel, gum and often jelly-like components of foods like oats, legumes and apples. Soluble fibre can lower your body’s glycemic response to a food by slowing down the time it takes for food to pass through the stomach and small intestine. Insoluble fibres are dry and bran-like and often referred to as roughage. All cereal grains and products made from them that retain the outer coat of the grain are sources of insoluble fibre. But not all foods containing insoluble fibre are low GI. Why? Insoluble fibres will only lower the GI of a food when they exist in their intact, original form, for example in whole grains of wheat. Here they act as a physical barrier, delaying access of digestive enzymes and water to the starch within the cereal grain.
Why do some high fibre foods have a low GI and not others?
Many processed grain foods that are rich in fibre such as wholemeal bread have a high GI. Why? It all comes down to the physical state of the fibre and the starch in the food. When wheat fibre has been finely divided as it is in wholemeal bread or breakfast cereals, it does little for either constipation or blood glucose levels. That’s why we say to choose your carbs carefully, and if your favourite wholegrain food has a high or moderate GI, combine it with a low GI food to reduce the glycemic load of your meal or snack.
The jury’s still out on cinnamon
Lab research has suggested that cinnamon (Cinnamomum cassia) may make body cells more sensitive to insulin. Some small studies have also shown that cassia cinnamon can reduce the blood glucose rise after eating. But it's too soon to recommend people with diabetes tuck into this spice and think it will steady their blood glucose levels naturally, according to researchers from University of Oklahoma in September Diabetes Care. In this latest study, 43 adults with type 2 diabetes were randomly given either cinnamon capsules or a placebo every day for three months. The cinnamon group took two capsules a day, each of which contained 500 milligrams of the spice. The placebo group took capsules containing wheat flour. In the end, there were no significant differences in glucose, cholesterol, A1C or insulin levels according to the researchers led by Dr Steve M. Blevins.
The reason for the conflicting findings from this and earlier studies may have to do with differences in the study groups according to Blevins and his colleagues. Most of the volunteers in the current study, for example, were on various diabetes drugs; in Khan’s 2003 study that found cinnamon reduced blood glucose levels, none of the participants were on any of these drugs. The researchers conclude that we need more studies to see whether factors such as diet, ethnicity, BMI, glucose levels, cinnamon dose and concurrent medication might affect cinnamon responsiveness. ‘Until then,’ they conclude, ‘cinnamon cannot be generally recommended for treatment of type 2 diabetes in an American population.’
– Diabetes Care 30:2236-2237, 2007